/ Recommend me a hydration pack

Santa was most generous this year and brought me a new Deuter Guide 35+ rucsac. I'd like to get a hydration pack to use with it, but have never used them before.
Does anyone have any recommendations or tips on what I should be looking for in a good one please?
Thanks,
Cari

In reply to carievans67:
I use platypus ones, which I like but are not the most popular. Stuck with them for replacements as I have all the fittings, cleaning kit and different sizes which are all interchangeable. Also against the grain I have the narrow neck ones . The bladder part lasts over 5yrs before it starts to delaminate - as long as you don't use them to break your fall on to rocks! I've burst two by high impacts!
Suggest you look for large opening ones for easy filling and cleaning, not that I have had any problems with mine. I store in the freezer between uses, and only sterilise once a year. Other things to look out for are mouth piece ease of use with say gloves on, insulating tube if you are to use in winter, mouth piece cover to stop dirt contamination, and general shape. With the latter do you want it to stand up itself, does it fit the rucksac etc.
Overall, I'm sticking with platypus despite it not being the easiest to fill and clean (being the narrow neck ones. I assume the large opening ones are easier). They work well in practice, have all the accessories, fits my rucksack well, and only once had it frozen up.

I got a really expensive msr one after going through several cheap plastic ones last summer. Apparently it's cordura, and also works as stand alone resivoir bag. Outdoorgearlab reckoned it was one of their top products anyone had used, and I'm inclined to agree. The tube join isn't exactly low profile but it fits in all my bags - osprey, black diamond and north face. It's also a funny shape with 4l in it, but then I very rarely carry that much.

In reply to carievans67: I am happy Camelbak Antidote user. Can't really compare with anything else as it is only second hydration bladder (the first one was cheap and water tasted like plastic - used that bladder only once).

Few suggestions:
1. Removable hose might be practical.
2. Wide opening is a must (in my opinion). It just makes cleaning, refilling and other things easier.
3. Valve locking mechanism is useful too. Antidote has it, but once I was descending via South-West side of Carn a'Mhaim and it was quite steep slope, to be honest. I touched the rock with my chest and then I realised that I also "pressed" the valve and it started to leak on my chest. Although it was not THAT risky, I suddenly realised that as soon as water had reached my boots, I would be in trouble.

If you also plan to use it in winter, neoprene sleeve would be useful, too. I noticed that after I refill the pack with chilly water from the streams, the water which is in the hose gets warm in the Summer. I suspect it might freeze in the Winter! In that case, you can actually blow some air through the valve and that way you fill the hose with air. It works, but after a while your hydration bladder will have much air in it. Also, after you refill you can put your bladder upside down and then suck all the air which was left in the bladder. Works well with my Antidote if I don't have much space in the rucksack.

Source has been the best for me after using three systems over the past 12 years.
Been using their widepac 2l for the past 18 months and only cleaned it once so far. Their grunge guard tech really does work.
Make sure you blow back whatever is in the tube to prevent it freezing during winter time. Handy tip I picked up here on this forum.

I have a couple for lowland use (I have a travel tap for mountains - far lighter), brands are generally better than shop's-own make.

they can become like trigger's broom - replacing pipes, lids, bags, taps, bite valves though.. so make sure you can get parts.

I store mine dismantled in my boiler cupboard (always warm, always bone dry) but a thorough soaking in milton tablets works a treat if you want to be certain (stuff which sterilises baby food containers, found in boots baby section)